How to communicate Server to Client with SignalR in Nancy with ASP.NET Hosting?

Question

Most of the examples I've found for SignalR are assuming ASP.NET (MVC or not). I'm using NancyFX. I'm having just one problem, so I'm hoping there's something I'm overlooking or some thing I need to do in Nancy to compensate for not being ASP.NET.

My one goal is to be able to notify the client browsers when a server event happens. I don't plan on replacing my Nancy routes with hub methods. But I would like the ability to call into the browser from my routes (actions).

I have very simple Hub that I created following the example in the SignalR Wiki. I'm not even sure I need it, since I don't plan on calling client to server.

public interface IUserNotifier
{
    void Start();
    void Notify(object @event);
}

I used an interface in hopes that I would be able to inject the same hub later on to use in my nancy routes... I'm not sure that is in the cards.

[HubName("userNotifier")]
public class UserNotifier : Hub, IUserNotifier
{        
    public void Start()
    {
        Notify(new {Status = "Started"});
    }

    public void Notify(object @event)
    {
        Clients.notification(@event);
    }
}

When I have the following code in my html file, I can see that it executes the Start() method, and then the Notify() method, delivering content to my client.

var communicator = $.connection.userNotifier;

$.extend(communicator, {
    Notification: function(event) {
        alert("notification received from server!");
        console.log(event);
    }
});

$.connection.hub.start()
    .done(function() {
        communicator.start();
});

Like I said, "starting" the hub works and sends a notification to the client. Very cool. But, then, my primary goal hasn't been accomplished yet. I need to initiate these notifications from other places in my code where they might not be directly associated with a "request".

I tried injecting my IUserNotifier in my nancy modules for use in the routes, but when the Notify() is fired, I get:

That's because the Clients property on the Hub base class is null (hasn't been initialized). So, I switched gears. I tried to follow multiple examples, including the example from the wiki page about hubs in the section called "Broadcasting over a Hub from outside of a Hub":

public class NotifierModule : NancyModule
{
    public NotifierModule(){

        Get["/notify/{message}"] = p => { 
            var context = GlobalHost.ConnectionManager.GetHubContext<UserNotifier>();
            context.Clients.notification(new { Message = p.message });
        };
    }
}

My Nancy route executes without throwing errors. Except my browser never receives the message. If I set a breakpoint in the route, I can see that Clients is initialized. Maybe the collection of clients is initialized but empty. Who knows? Maybe you do. :)

Again, my main goal is to be able to send events/notifications to the browser from anywhere in my code, any time. Is that too much to ask? What should I be doing here?

Answer 1

I'm sure you must have found the answer already. However, I figured I could try and help out in case anyone else runs into a similar problem. In order for your server on the .NET side to send messages to clients, it would also need to have a connection made to the hub.

var connection = new HubConnection("http://localhost/");
connection.Start();
connection.Notify("Hello");

Check out an official example at:

https://github.com/SignalR/SignalR/blob/master/samples/Microsoft.AspNet.SignalR.Client.Samples/Program.cs